News aggregators are not hosting the actual content, which is very key to the design. For news articles, usually you want to post a small blurb or a picture, where as a news aggregator is nothing but the title.
News websites also need to maintain visual continuity between the navigation and the articles themselves, while aggregators only need to design navigation.
I don't see your point. News sites want to post a blurb and a picture, but reddits traffic tells me that users don't really care.
And a news site can still have a simple headline page AND consistent when you click through to the articles.
Also, I'm not saying there's no room to add emphasis and prominence to some articles, but I am saying that the way they do it now makes no sense to me, and I'm a designer by trade.
Reddit, like HN, actually deals with a huge range of sources where all the content is written very differently.
News sites are written consistently. All news stories follow the same format, with the first paragraphs summarising the story. The news site knows if a picture in the story is relevant.
Reddit & HN actually tell us nothing about the best format for news because they quite literally can't serve their links up in a format like this. Each source is too different.
Though I also think it's too busy. But I do not agree at all that HN or Reddit can tell us anything about news sites.
News websites also need to maintain visual continuity between the navigation and the articles themselves, while aggregators only need to design navigation.